This application is based on and incorporates herein by reference Japanese Patent Application No. 2002-94059 filed on Mar. 29, 2002.
1. Field of the Invention
The present invention relates to a monitor system that monitors leakage of compressed air in a compressed air circuit installed in, for example, a manufacturing facility.
2. Description of Related Art
Air-driven devices, such as air cylinders, that use compressed air as its drive source are used in, for example, various manufacturing facilities.
Generally, a plurality of air-driven devices is connected to a single supply line, which extends from a compressed air source, to form a compressed air circuit.
Currently, it is difficult to completely and permanently eliminate leakage of compressed air at a connection of each air-driven device connected to the compressed air circuit. Thus, all of the air-driven devices need to be periodically inspected for leakage of compressed air to manage leakage of compressed air in the compressed air circuit. Specifically, the leakage of compressed air is detected by an operator through use of some or all of the human senses, for example, by listening to sound of leaked air from each air-driven device or by feeling air pressure of leaked air from each air-driven device with a hand. Then, the operator may determine whether repair work is needed based on the inspection result. Alternately, the leakage of compressed air can be determined as follows. That is, when the leakage of compressed air becomes severe, the corresponding air-driven device may malfunction. At that time, because of the malfunction of the air-driven device, the operator can notice the leakage of compressed air for the first time. When the operator notices the leakage of compressed air, the corresponding manufacturing facility may be stopped, and the corresponding portion, from which compressed air leaks, may be repaired.
However, the above leakage management operations of compressed air pose the following disadvantages.
That is, since the periodic inspection of the air-driven devices depends on the human senses and needs to be performed on all of the air-driven devices, the number of steps involved in the inspection is relatively large. Furthermore, the periodic check of leakage of compressed air poses the following disadvantage. That is, if the leakage of compressed air starts during a time interval between one inspection operation and the next inspection operation, this leakage of compressed air cannot be detected unless it causes malfunction of the corresponding air-driven device. Thus, wasteful compressed air is kept consumed until the next periodic inspection and subsequent repair work are performed.
When the degree of leakage of compressed air becomes severe, and thus the corresponding air-driven device malfunctions, the facility, in which the malfunctioning air-driven device is installed, needs to be stopped immediately, and the corresponding repair work needs to be performed. This normally causes a delay in the operational plan of the facility, resulting in a reduction in a working ratio of the facility.
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a compressed air monitor system, which continuously monitors leakage of compressed air in a corresponding facility to allow a reduction in the number of inspection steps and to restrain sudden stop of the facility and wasteful consumption of compressed air in the facility.
To achieve the objective of the present invention, there is provided a compressed air monitor system that monitors leakage of compressed air in at least one compressed air circuit, each of which includes a supply line of compressed air and a plurality of air-driven devices. The air-driven devices are connected to the supply line and are driven by compressed air supplied through the supply line in each compressed air circuit. The compressed air monitor system includes at least one flow meter and a monitor computer. Each flow meter is installed in the supply line of a corresponding one of the at least one compressed air circuit and measures a flow rate of compressed air, which indicates an amount of compressed air that passes through the corresponding supply line per unit time. Each flow meter outputs the measured flow rate of compressed air as measured flow rate data. The monitor computer receives the measured flow rate data from each flow meter. The monitor computer includes an operational state identifying means for identifying a current operational state of the air-driven devices of each compressed air circuit from a plurality of categorized operational states of the air-driven devices. The monitor computer further includes an air leakage determining means for determining a level of leakage of compressed air in each compressed air circuit through comparison of the measured flow rate data of the corresponding compressed air circuit with a corresponding one of a plurality of master flow rates, which corresponds to the current operational state of the air-driven devices identified by the operational state identifying means. Each of the plurality of master flow rates is set for a corresponding one of the categorized operational states of the air-driven devices and is used as a reference flow rate of compressed air in the corresponding one of the categorized operational states of the air-driven devices.